Generally, it is known that various size dies may be interchangeably connected to the head of an extruder barrel. These dies are utilized to manufacture various types of extruded polymeric parts. When it is desired to make a different part, a clamping mechanism is uncoupled to release the die, a new die is installed and the clamping mechanism is re-engaged. An example of a clamping device for an extruder head is disclosed in Christy et al. U.S. Pat. No. 3,632,279 which shows the overall arrangement of two semi-circular, double-pivoted clamps for an extruder die with the clamp section pivotally secured to the die head and wherein a die holder is pivoted to the extruder cylinder.
Other clamping devices, as seen in Meehan U.S. Pat. No. 2,057,043 and Hutchinson U.S. Pat. No. 2,673,102, show two 180.degree. clamp portions with double pivots.
Yet another series of clamping devices, as seen in Abbes et al. U.S. Pat. No. 4,341,406 and Bormioli U.S. Pat. No. 4,354,522, disclose a plurality of flange-clamping links that are double pivoted to intermediate connectors.
Other configurations of clamping devices are shown in LeDevehat U.S. Pat. No. 4,515,182 and Wolters et al. U.S. Pat. No. 4,036,258. The LeDevehat patent shows a three-piece pivoted clamping collar for camming tapered flanges wherein one of the clamp portions is pivotally secured to a frame member. The patent to Wolters discloses pivot pins that are pivoted to a frame member.
Although the above-disclosed devices are suitable for securing a die to an extruder head, it will be appreciated that each has inherent drawbacks. Typically, the disclosed devices may not compensate for poor dimensional stability in the mating parts. As a result, inadequate pressure may be maintained in the extruder head which results in a less than desirable extruded part. In other words, inadequate pressure in the extruder head may even require compensation in other processing variables by adjusting heat zones, the speed of the extruder screw, and the like to ensure an acceptable extruded part.
Still another problem with the disclosed dispensing devices is that if an inadequate seal is created between the die and the extruder barrel polymeric material may leak and interfere with the extrusion process. It will also be appreciated that a leaky connection between a die and an extruder barrel causes a mess and produces excess scrap material.
Therefore, it has become apparent that it is desirable to provide a locking gate for an extruder which applies a uniform or evenly distributed sealing force around the die when it is connected to the extruder barrel. It is also desirable that the locking gate provide a biasing force to one of the clamshells to control its range of motion.